Transport of stereoscopic image data over a display interface

ABSTRACT

A digital display interface ( 40 ) connects a first audio-visual device ( 10 ) to a second audio-visual device ( 20 ). Stereoscopic image data is transmitter over the display interface ( 40 ). Components of stereoscopic image data are multiplexed and inserted into an image data carrying element. An existing deep color mode can be re-used for this purpose. Signaling information to help identify or decode the stereoscopic image data is carried in auxiliary data carrying elements. Stereoscopic image data can be distributed between image data carrying data elements and auxiliary data carrying data elements. Auxiliary data carrying elements can be transmitted in horizontal or vertical blanking periods, and can comprise HDMI Data Island Packets. Stereoscopic image data can be sent over an auxiliary data channel. The auxiliary data channel can form part of the same cable as is used to carry a primary channel of the display interface, a separate cable, or a wireless link.

FIELD OF THE INVENTION

This invention relates to transport of image data for the display ofstereoscopic images.

BACKGROUND TO THE INVENTION

Various schemes for displaying three dimensional images (static, ormoving images) are known. One well-known scheme simultaneously displaystwo images which are encoded for the left eye and right eye by means ofdifferent optical polarizations, or colors (e.g. red and green). Aviewer wears a pair of special glasses which have lenses in front of theleft and right eyes. The lenses are arranged to pass only the imageintended for that eye, i.e. a left eye sees only the image intended forthat eye. Another stereoscopic display technique sequentially presentsan image intended for the left eye, and an image intended for the righteye. A user wears a special pair of glasses which are shuttered insynchronism with the displayed images, such that the left eye shutter isopen during the period when the left eye image is displayed, and theright eye shutter is open during the period when the right eye image isdisplayed.

Auto stereoscopic display techniques remove the need for a viewer towear special glasses. One known scheme uses a flat panel display withmultisided slanted ventricular lenses mounted in front of displayelements. An example of this kind of display is described inWO07/069,195 A2.

Historically, 3D displays have been limited to specialized applications(e.g. medical imaging) or feature film presentation where it is possibleto provide bespoke, high cost, display apparatus. There is nowconsiderable interest in delivering stereoscopic content to a much wideraudience, including the consumer electronics market. However, an issuewith delivering stereoscopic images in a consumer electronicsenvironment is that conventional displays, and display interfaces whichconnect displays or projectors to media players, have been designedspecifically for the display of conventional 2D images.

Schemes for conveying stereoscopic image data within the confines ofexisting display interfaces have tended to sacrifice part of the activeportion of an image to carry additional data necessary to render astereoscopic image. The WOWvx format developed by Koninklijke PhilipsElectronics N.V. divides the overall display frame into a number ofseparate regions where different data can be carried. The overall frameis divided into two sub-frames, arranged side-by-side: a first of thesub-frames carries 2D image data and a second of the sub-frames carriesdepth information. A header is added to the beginning of the upperleft-hand corner of the frame. The image data is carried in a normalmanner across a display interface. A display extracts depth data fromthe second sub-frame and creates a 3D image having a resolution of thefirst sub-frame. This 3D image can then be ‘stretched’ to occupy thefull visible area of the display.

Digital displays and media players are increasingly being equipped withdigital display interfaces such as the High Definition MultimediaInterface (HDMI). The present invention seeks to provide an alternativeway of delivering stereoscopic image data over a digital displayinterface.

SUMMARY OF THE INVENTION

A first aspect of the present invention provides a digital displayinterface part for use in a first audio-visual device for supporting adigital display interface between the first audio-visual device and asecond audio-visual device, the interface part comprising:

an input for receiving image data;

a formatter arranged to format the data for transport over theinterface, wherein the formatter is operable in:

-   -   a first mode in which the formatter generates a stream of first        data elements which carry pixel data of a 2D image;    -   a second mode in which the formatter generates a stream of        second data elements which carry a multiplexed combination of        components of a stereoscopic image.

An advantage of this arrangement is that the stereoscopic image data canbe carried across a digital display interface using the existingcapacity of the interface. Advantageously, where the display interfacesupports various color depths of image data, such as 48-bit color aswell as conventional 24-bit color, the higher capacity transport modeswhich are intended to transport higher color depth data can be re-usedto carry the multiplexed stereoscopic image data. Therefore, noadditional capacity is required from the interface to carry thestereoscopic data, while still allowing good color depth for thestereoscopic content. It also has the benefit that little or no changesare required to an existing standard defining the display interface. Italso allows stereoscopic image content to be sent with a resolutionwhich is significantly higher than schemes which sacrifice part of theactive image area to carry the stereo image data.

Advantageously, the second data elements have a capacity which is nogreater than, and preferably the same as, the first data elements. Thisallows the stereoscopic data to be carried with minimal modification tothe standards defining the interface.

The term “stereoscopic image data components” is intended to include anyscheme which sends data to construct a stereoscopic (orautostereoscopic) display to a user, and includes: schemes which sendleft eye image data and right eye image data; schemes which send 2Dimage data and image depth data; schemes which send 2D image data andimage depth data and occlusion information, indicating which objects inthe picture are occluded by other objects.

In the case of a stereoscopic image which uses left eye and right eyeimage data, the formatter can use a portion of the second data elementto carry the left eye image data and another portion of the second dataelement to carry the right eye image data.

In the case of a stereoscopic image which uses 2D+depth data, theformatter can use a portion of the second data element to carry the 2Dimage data and another portion of the second data element to carry theimage depth data. The depth data may additionally be carried in otherparts of a signal, such as periods within horizontal or verticalblanking periods. In HDMI, Data Island Packets are carried within theseperiods, and certain Data Island Packets can be identified as carryingdepth data.

Advantageously, signaling information is sent across the interfaceidentifying which mode the formatter is using and further signalinginformation can allow the second audio-visual device (e.g. a display orprojector) to indicate whether it has the capability to renderstereoscopic data sent in that formatting mode.

In a High Definition Multimedia Interface (HDMI), signaling can becarried by packets carried within the Data Islands between image data.The capability of a sink device to handle stereoscopic data can besignaled between interface parts using the HDMI Display Data Channel(DDC) channel, with capability data being stored in an Extended DisplayIdentification Data (EDID) ROM at a sink.

A related aspect of the present invention provides a digital displayinterface part for use in an audio-visual device for supporting adigital display interface between the audio-visual device and anotheraudio-visual device, the interface part comprising:

an input for receiving formatted image data from the interface;

a processor arranged to extract image data, the processor being operablein:

-   -   a first mode in which the processor extracts pixel image data        for a 2D image from a stream of first data elements; and,    -   a second mode in which the processor demultiplexes components of        a stereoscopic image from a stream of second data elements which        carry a multiplexed combination of components of a stereoscopic        image.

A related aspect of the present invention provides a method offormatting image data at a digital display interface part of a firstaudio-visual device for transport over a digital display interfacebetween the first audio-visual device and a second audio-visual device,the method comprising:

receiving image data;

formatting the image data for transport over the interface by:

-   -   in a first mode, generating a stream of first data elements        which carry pixel data of a 2D image; and,    -   in a second mode, generating a stream of second data elements        which carry a multiplexed combination of components of a        stereoscopic image.

A related aspect of the present invention provides a method ofprocessing image data at a digital display interface part of anaudio-visual device, the method comprising:

receiving formatted image data from the interface;

extracting image data by:

-   -   in a first mode, extracting pixel image data for a 2D image from        a stream of first data elements; and,    -   in a second mode, demultiplexing components of a stereoscopic        image from a stream of second data elements which carry a        multiplexed combination of components of a stereoscopic image.

A further aspect of the invention provides a digital display interfacepart for use in a first audio-visual device for supporting a digitaldisplay interface between the first audio-visual device and a secondaudio-visual device, the interface part comprising:

an input for receiving stereoscopic image data;

a formatter arranged to format the data for transport over theinterface, wherein the formatter is operable to send a portion of thestereoscopic image data over a primary image data transport channel ofthe interface and another portion of the stereoscopic image data over anauxiliary data channel.

The interface part can send signaling information across the interfaceidentifying how stereoscopic data is distributed between the primarydata channel and the auxiliary data channel.

Advantageously, the stereoscopic image data comprises 2D image data andimage depth data and the formatter is arranged to send depth data acrossthe auxiliary data channel.

The auxiliary data channel can comprise a separate line, or lines,within the same cable as the primary channel; a second cable which isseparate from a first cable carrying the primary channel; or a wirelesslink.

A related aspect of the present invention provides a digital displayinterface part for use in an audio-visual device for supporting adigital display interface between the audio-visual device and anotheraudio-visual device, the interface part comprising:

an input for connecting to a primary image data transport channel of theinterface and an auxiliary data channel;

a processor arranged to extract a portion of the stereoscopic image datafrom the primary image data transport channel of the interface andanother portion of the stereoscopic image data from the auxiliary datachannel.

A related aspect of the present invention provides a method of sendingstereoscopic image data over a digital display interface between a firstaudio-visual device and a second audio-visual device, comprising, at thefirst audio-visual device:

receiving stereoscopic image data for transport over the interface;

sending a portion of the stereoscopic image data over a primary imagedata transport channel of the interface and another portion of thestereoscopic image data over an auxiliary data channel.

A related aspect of the present invention provides a method ofprocessing stereoscopic image data at an audio-visual device forsupporting a digital display interface between the audio-visual deviceand another audio-visual device, the method comprising:

extracting a portion of the stereoscopic image data from a primary imagedata transport channel of the interface and another portion of thestereoscopic image data from an auxiliary data channel.

A further aspect of the invention provides a digital display interfacepart for use in a first audio-visual device for supporting a digitaldisplay interface between the first audio-visual device and a secondaudio-visual device, the interface part comprising:

an input for receiving stereoscopic image data;

a formatter arranged to generate a stream of image data carrying dataelements and auxiliary data carrying data elements at intervals in thestream, and wherein signaling information for use in decoding thestereoscopic image data is carried in at least one of the auxiliary dataelements.

Where the stereoscopic image data comprises left eye image data andright eye image data, the signaling information can specify what dataelements carry the left eye image data and what data elements carry theright eye image data. Where the left eye images and right eye images areinterleaved on a line-by-line basis, the signaling information can besent as often as once for each pair of interleaved lines, although itcan be sent much less frequently, such as once per field or frame.

Where the stereoscopic image data comprises 2D image data and depthinformation, the signaling information can specify at least one of: thetransmission location, quantity of the depth information.

Advantageously, where the stereoscopic image data has a plurality ofdifferent possible formats, the signaling information specifies theformat. One of the formats for the stereoscopic image data can be ascheme which encodes the stereoscopic image data within a conventional2D image format.

Advantageously, the signaling information is carried in a horizontal orvertical blanking period and for a High Definition Multimedia Interface(HDMI) the signaling information can be sent in a Data Island Packet.

A related aspect of the present invention provides a digital displayinterface part for use in an audio-visual device for supporting adigital display interface between the audio-visual device and anotheraudio-visual device, the interface part comprising:

an input for receiving, from the interface, a stream of image datacarrying data elements and auxiliary data carrying data elements atintervals in the stream;

using signaling information carried in at least one of the auxiliarydata elements to decode the stereoscopic image data.

A related aspect of the present invention provides a method of sendingstereoscopic image data over a digital display interface between a firstaudio-visual device and a second audio-visual device comprising, at thefirst audio-visual device:

receiving stereoscopic image data;

generating a stream of image data carrying data elements and auxiliarydata carrying data elements at intervals in the stream, and whereinsignaling information for use in decoding the stereoscopic image data iscarried in at least one of the auxiliary data elements.

A related aspect of the present invention provides a method ofprocessing stereoscopic image data at a digital display interface partof an audio-visual device, the method comprising:

receiving, from the interface, a stream of image data carrying dataelements and auxiliary data carrying data elements at intervals in thestream;

using signaling information carried in at least one of the auxiliarydata elements to decode the stereoscopic image data.

A further aspect of the invention provides a digital display interfacepart for use in a first audio-visual device for supporting a digitaldisplay interface between the first audio-visual device and a secondaudio-visual device, the interface part comprising:

an input for receiving stereoscopic image data components;

a formatter arranged to generate a stream of image data carrying dataelements and auxiliary data carrying data elements at intervals in thestream, and wherein the stereoscopic image data is distributed betweenthe image data carrying data elements and the auxiliary data carryingdata elements.

Advantageously, the stereoscopic image data components are 2D image dataand image depth data and wherein the depth data is carried in theauxiliary data carrying data elements. Advantageously, the streamfurther comprises signaling information, carried within auxiliary datacarrying data elements, specifying which part of an image the depthinformation relates to.

The auxiliary data carrying data elements are sent in a horizontal orvertical blanking period, such as HDMI Data Island Packets.

A related aspect of the present invention provides a digital displayinterface part for use in an audio-visual device for supporting adigital display interface between the audio-visual device and anotheraudio-visual device, the interface part comprising:

an input for receiving, from the interface, a stream of image datacarrying data elements and auxiliary data carrying data elements;

a processor arranged to extract stereoscopic image data from the imagedata carrying data elements and at least part of the stereoscopic imagedata from the auxiliary data carrying data elements.

A related aspect of the present invention provides a method of sendingstereoscopic data across a digital display interface between a firstaudio-visual device and a second audio-visual device, the methodcomprising, at the first audio-visual device:

receiving stereoscopic image data components;

generating a stream of image data carrying data elements and auxiliarydata carrying data elements at intervals in the stream, and distributingthe stereoscopic image data between the image data carrying dataelements and the auxiliary data carrying data elements.

A related aspect of the present invention provides a method ofprocessing stereoscopic image data at a digital display interface partof an audio-visual device, the method comprising:

receiving, from the interface, a stream of image data carrying dataelements and auxiliary data carrying data elements;

extracting stereoscopic image data from the image data carrying dataelements and at least part of the stereoscopic image data from theauxiliary data carrying data elements.

The functionality described here can be implemented in software,hardware or a combination of these. The invention can be implemented bymeans of hardware comprising several distinct elements, and by means ofa suitably programmed computer. Accordingly, further aspects of theinvention provide software for implementing any of the methods. Thesoftware may be stored on an electronic memory device, hard disk,optical disk or other machine-readable storage medium. The software maybe delivered as a computer program product on a machine-readable carrieror it may be downloaded to the AV device via a network connection.

The invention also extends to signals, for transmission over the displayinterface, which result from any of the methods.

Features of the various aspects of the invention can be combined.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be described, by way of example only,with reference to the accompanying drawings in which:

FIG. 1 shows a display interface for carrying image data between two AVdevise;

FIG. 2 shows a formatting function at one end of the interface;

FIG. 3 shows a conventional way of sending 2D image data across adisplay interface;

FIGS. 4 and 5 show ways of sending stereoscopic image data across adisplay interface;

FIG. 6 shows format of an HDMI video frame; and,

FIG. 7 shows a display interface which includes an auxiliary datachannel.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows an example scenario in which the invention can be used. InFIG. 1, an AV device 10 which is capable of providing a source ofdigital AV content is connected to a display (or video projector) 20 viaa digital display interface (DDI) 40. Interface parts 12, 22 in devices10, 20 support the interface 40, and provide functions such asformatting signals into the form required by standards defining theinterface 40. The source device 10 can be a device which can retrievedigital AV content from a store 11, such as a hard disk, a solid statememory or an optical disc or any other fixed or removable storage mediumor device. Examples of device 10 include a personal video recorder(PVR), an optical disc player such as a DVD player, an HD-DVD player ora Blu-ray player. Alternatively, device 10 can take the form of aset-top box which receives content from a distribution channel (such asa broadcast channel or broadband network or other type of network (e.g.home network)).

There are a variety of methods for displaying stereoscopic (3D) images.The two main methods for transferring 3D image data across an interfaceare: to transmit two complete, separate, stereoscopic imagesrepresenting the left and right views as seen by human eyes; and anormal 2D image with associated depth information that can be used togenerate the stereoscopic images within the display. The first methodgenerally requires a significantly higher bandwidth (up to twice thatneeded for a 2D image) over the interface, but needs little processingin the display, while the second method can require a smaller increasein bandwidth, but at the expense of some fast real-time processing inthe display to process the depth information.

Current digital display interfaces, such as HDMI, offer a very highbandwidth. These interfaces transfer uncompressed pixel information,unlike other transport mechanisms (such as Ethernet, USB, IEEE1394)which have to transfer compressed images because of their bandwidthlimitations. Originally, images transferred by HDMI were limited to 8bits per color per pixel, so-called “24-bit color”. Improvements to HDMIfrom version 1.3 have allowed HDMI to carry more bits per pixel, withthe options of carrying 10, 12 and 16 bits per color per pixel, i.e. upto 48-bit color. HDMI describes Deep Color Pixel Packing modes (HDMI1.3a, section 6.5.3) which allow the higher color depths just described.

According to one embodiment of the present invention, the deep colormodes are used to transport stereoscopic image data. The stereoscopicimage data can be left image data+right image data or 2D+depthinformation. FIG. 2 shows a formatting function 15 used within aninterface part 12. The formatter 15 can selectively operate in one of anumber of different modes. This is shown schematically by formatterselecting one of the sets of inputs: 2D image data 31; 2D+depth imagedata 32, 33; or left eye and right eye image data 34, 35 for processingand selectively connecting 38 to an interface output 39. Formatter 15can receive conventional 2D image data 31, such as 24-bit color imagedata 31. Typically this is received in an RGB or component video(Y,Cr,Cb) format. When receiving stereoscopic image data, formatter 15multiplexes 36, 37 the image data components. For left eye/right eyeimage data, the left eye data and right eye data will typically be takenfrom the same pixel in the left eye/right eye frames or fields of theimages, although other algorithms for combining pixels are also withinthe scope of the present invention. For 2D image+depth information, the2D image data will typically correspond to a single pixel (e.g. RGB orcomponent video format) and the depth information can take a differentform, and may correspond to a different region of the image to the pixelof the 2D image. The formatter 15 may only support one of the 3D formats(i.e. just L+R, or just 2D+depth) or both types of 3D format.

FIGS. 3 to 5 show a range of different ways in which the image data canbe multiplexed. FIG. 3 shows conventional image data. In HDMI, the threecolor components (R,G,B or Y,Cr,Cb) are sent simultaneously on threeTransition Minimised Differential Signaling (TMDS) channels 41. TMDSrefers to line-level coding applied to the data to maintain anapproximate DC balance as well as a reduction in the number oftransitions in the data stream. Each color component can be sent using astandard color depth (e.g. 8 bits per color per pixel) or an enhancedcolor depth, such as 16 bits per color per pixel. FIG. 4 shows a way inwhich stereoscopic left eye/right eye data can be multiplexed. Thecomponents of the left eye data (R,G,B or Y,Cr,Cb) are sent in a firstportion of each data-carrying element, and then immediately followed bythe components of the right eye data (R,G,B or Y,Cr,Cb). Both left eyeand right eye are either sent within the same packet, consecutive imagedata packets, or parts of consecutive image data packets. As an example,where a 16-bit per color per pixel mode is used, bits 0-7 can carry theleft image Y data and bits 8-15 carry the right image Y data. HDMI 1.3acurrently allows a color depth of up to 16-bits per color per pixel(48-bit color). FIG. 4 shows how two 24-bit color images can be carriedwithin the existing 48-bit color mode with no additional capacityrequired from the interface. It will be appreciated that futurerevisions of HDMI (and other) specifications may extend the bandwidth topermit a larger color depth, which will allow each of the left eye andright eye images to use more bits per pixel, so allowing richer 3Dimages.

FIG. 5 shows a scheme for sending 2D image data+depth information wherethe 2D data is sent first, followed by the depth data. Each colorcomponent (R,G,B or Y,Cr,Cb) follows the same format. In FIG. 6 thecapacity of the packet is divided equally between the 2D data and depthinformation, although any other division is possible. It may be possibleto send significantly less depth data than 2D data, which can allow the2D image to use a wide color palette and/or high resolution. It is alsopossible to send some—or all—of the depth information in a differentpart of the transmitted data stream, such as within specific HDMI DataIsland Packets carried within the horizontal and vertical line blankingintervals. This is particularly useful for depth data that is notattached directly to a specific pixel, for instance, it applies to aregion of the image.

Interface part 12 sends signaling 42 which indicates the format of theimage data, e.g. indicating whether the image data is 2D, stereo (L+R)or stereo (2D+depth). The signaling can also indicate further details ofthe multiplexing scheme, such as which color depth mode is being used tocarry the multiplexed data, the number of bits per data element that areallocated to 2D data and the number of bits per data element that areallocated to depth data. This signaling allows flexibility in how thestereo data is allocated to data carrying elements sent across theinterface 40 and allows for the amount of Depth information to bechanged dynamically, according to the requirements of the content whichis to be displayed. In HDMI, Data Island Packets are sent in horizontaland vertical line blanking periods. The signaling information canconveniently be carried within a Data Island Packet. FIG. 6 shows thelayout of an HDMI video frame, showing a region 61 where pixel data issent across TMDS channels, a horizontal blanking period 63 and avertical blanking period. Data Island Packets 64 are sent within DataIsland periods positioned within the horizontal and vertical blankingperiods 62, 63. The signaling data can be carried in a General ControlPacket, an Auxiliary Video InfoFrame (AVI) packet or an InfoFrame Packetspecifically designated for this purpose. If depth data is carried bothwithin the pixel data carrying data elements and other places of thestream, the signaling can indicate where the depth data is to be found.The amount of depth data and the location(s) of the depth data can varyon a dynamic basis during an image, or sequence of images, depending onthe required color depth, resolution or complexity of the image (e.g.the amount of depth information within an image).

AV device 20 includes a processor 21 applies suitable processing to thedata to render a 3D image. In the case of stereoscopic display, where auser is simultaneously or sequentially presented with separate left andright eye images, processor 21 constructs the separate left eye/righteye images and outputs them 24 at the required time. For sequentialstereoscopic displays, a further output 23 is provided to synchronizeoperation of shuttered glasses. In the case of an autostereoscopicdisplay, such as a display using a ventricular screen, processor 21constructs the image data which is required to be output 24 to thedisplay elements to generate the autostereoscopic display. Interfacepart 22 and processor 21 use the signaling information sent across theinterface to:

determine if stereoscopic image data is being sent; determine whatgeneral stereoscopic image format is being used (e.g. left+right image;2D+depth; stereo encoded within active image data);

determine more detail of how the image data is being encoded on theinterface, and therefore what decoding scheme should be used at thereceiver. This may include information about which deep color mode isbeing used, bit allocation between 2D and depth data, transmissionlocation of depth data (e.g. specific Data Island Packets or auxiliarychannel locations).

Further signaling between the AV devices 10, 20 allows the sink device20 to indicate it's capabilities to receive and process image data. Thecapability information may indicate the maximum allowed bandwidth foreach mode of sending 2D and stereo image data. In HDMI, the capabilityof a sink device can use the Display Data Channel (DDC) channel, withcapability data being stored in an Extended Display Identification Data(EDID) ROM at a sink.

The interface may support other schemes for sending stereoscopic data. Afirst alternative is to send two separate complete images, carriedsequentially (such as a complete left image followed by a complete rightimage). The indication of the left and right image can be indicated bysignaling information carried directly adjacent the position of theimage data, such as an HDMI Data Island Packet.

A second alternative is to send two separate images, but with the linesof the two images interleaved. For example, the first line of the leftimage is sent first, followed by the first line of the right image, andso on.

A third alternative is to send a 2D image in a conventional manner, andto carry depth information in specific Data Island Packets dedicated tocarrying depth information.

In each of these alternatives, signaling information carried directlyadjacent the position of the image data, such as an HDMI Data IslandPacket, can indicate what the image data corresponds to. For the thirdalternative, the signaling information can specify which part of theimage the depth data relates to. As noted above, the HDMI Data IslandPackets can be a General Control Packet, an Auxiliary Video InfoFrame(AVI) packet or an InfoFrame Packet specifically designated for thispurpose. The information in these packets can identify:

the current stereoscopic method (field, line or byte) being used (seeabove);

whether a Deep Color Pixel Packing mode is being used to carry 3Dinformation or a Deep Color Mode 2D image;

the mapping of left and right images to the current field, line or byte;

how many of the Data Island Packet packets/sub-packets are being uses tocarry Depth information;

the location of other stereoscopic image data components.

The embodiments above show how the separate stereoscopic imagecomponents can be carried over a display interface. For someapplications, especially those intended for display on a ventricularscreen, the picture received at the interface part 12 may already beencoded with stereoscopic content. As an example, a WOWvx encoded imageas described in the background section, comprises a 2D image, depthinformation and/or occlusion information already embedded into separateregions of a conventional image. In one embodiment, the 2D image iscarried in one quarter of the image pixels (e.g. in half a line for halfthe total lines in the picture). The associated depth and/or occlusioninformation is carried in the other three-quarters of the presentedpicture. In this case, the lines of the picture are transported acrossthe HDMI link as thought they were a single 2D image occupying all ofeach line, for all the available lines. In order to identify such a 3Dimage, an HDMI Data Island Packet (typically a General Control Packet,Auxiliary Video InfoFrame (AVI) packet or specifically designatedInfoFrame Packet) indicates this method. The information in this Packetidentifies:

the current stereoscopic method (e.g. 2D+Depth) being used;

any information pertaining to this method which is required by thedisplay.

The sink identifies the transmitted picture as using this method andprocesses the picture accordingly. The sink also carries information inthe EDID indicating that it supports this method.

In the above description, stereoscopic image data is carried over achannel of an interface (e.g. an HDMI Transport Stream) either bymultiplexing the stereoscopic image data within normal data carryingelements of the channels, or by carrying at least part of thestereoscopic image data within other packets (e.g. Data Island Packets)carried over the same channel. A further embodiment of the inventioncarries at least some of the stereoscopic image data over an associatedhigh speed auxiliary data link such as Gigabit Ethernet, IEEE 1394 or ahigh-speed wireless link. Signaling information identifies whichinformation is carried by the primary channels of the interface andwhich is carried by the associated auxiliary link. In HDMI, thesignaling information can be carried in Data Island Packets. Similar, orcomplementary, identification information may also be carried on theassociated high speed auxiliary link. The sink uses the received DataIsland Packets to identify which information is carried on which linkand combines the two streams of data in the necessary format forpresentation or processing. Depending on the characteristics of the HDMIand associated auxiliary link, it may be necessary to buffer the datacontained in the two streams in order to maintain synchronicity betweenthem. In one embodiment using the above embodiment, the associated wiresfor the auxiliary link are carried within the HDMI cable; this option isshown in FIG. 7 by additional line 50 connecting modules 51, 52 ininterface parts 12, 22. In other embodiments, the associated auxiliarylink is carried in a separate cable connecting the devices 10, 20, or bya high-speed wireless link.

Other variations to the disclosed embodiments can be understood andeffected by those skilled in the art in practicing the claimedinvention, from a study of the drawings, the disclosure, and theappended claims. In the claims, the word “comprising” does not excludeother elements or steps, and the indefinite article “a” or “an” does notexclude a plurality. A single processor or other unit may fulfill thefunctions of several items recited in the claims. The mere fact thatcertain measures are recited in mutually different dependent claims doesnot indicate that a combination of these measured cannot be used toadvantage. Any reference signs in the claims should not be construed aslimiting the scope.

1-49. (canceled)
 50. A digital display interface part, for use in afirst audio-visual device for supporting a digital display interfacebetween the first audio-visual device and a second audio-visual device,the digital display interface for transmitting uncompressed pixelinformation, the interface part comprising: an input for receiving imagedata; a formatter arranged to format the data for transport over theinterface, wherein the formatter is operable in: a first mode in whichthe formatter generates a stream of first data elements, which carrypixel data of a 2D image; and, a second mode in which the formattergenerates a stream of second data elements which carry a multiplexedcombination of components of a stereoscopic image, wherein the interfacepart is arranged to send signaling information across the interface, thesignaling information identifying which mode the formatter is using. 51.An interface part according to claim 50, wherein the signalinginformation comprises information for enabling the second audio-visualdevice to determine a stereoscopic image format being used in the secondmode.
 52. An interface part according to claim 51, wherein the signalinginformation is carried in a horizontal or vertical blanking period. 53.An interface part according to claim 50, wherein the interface is a HighDefinition Multimedia Interface (HDMI) and the signaling information issent in a Data Island Packet between image data.
 54. An interface partaccording to claim 53, which is arranged to receive signalinginformation across the interface specifying capabilities of the secondaudio-visual device.
 55. An interface part according to claim 50,wherein the stereoscopic image data components are left eye image dataand right eye image data.
 56. An interface part according to claim 55arranged for sending the left eye image data and the right eye imagedata sequentially.
 57. An interface part according to claim 56, whereinan indication of the left and right image data being indicated bysignaling information carried directly adjacent a position of the imagedata.
 58. An interface part according to claim 55 arranged for sendingthe left eye image data and the right eye image data by lineinterleaving.
 59. An interface part according to claims 50, wherein thestereoscopic image data components are 2D image data and image depthdata.
 60. An interface part according to claim 58, wherein the formatteris arranged to use a portion of the second data element to carry the 2Dimage data and another portion of the second data element to carry theimage depth data.
 61. A digital display interface part for use in anaudio-visual device for supporting a digital display interface betweenthe audio-visual device and another audio-visual device, the digitaldisplay interface for transmitting uncompressed pixel information theinterface part comprising: an input for receiving formatted image datafrom the interface; a processor arranged to extract image data, theprocessor being operable in: a first mode in which the processorextracts pixel image data for a 2D image from a stream of first dataelements; and, a second mode in which the processor demultiplexescomponents of a stereoscopic image from a stream of second data elementswhich carry a multiplexed combination of components of a stereoscopicimage, the interface part arranged to receive signaling informationacross the interface, the signaling information identifying which modethe formatter is using.
 62. An interface part according to claim 50,wherein the signaling information comprises information for enabling thesecond audio-visual device to determine a stereoscopic image formatbeing used, the interface part arranged to determine a stereoscopicimage format being used.
 63. An interface part according to claim 50,wherein the interface is a High Definition Multimedia Interface (HDMI)and the signaling information is received in a Data Island Packetbetween image data.
 64. An interface part according to claim 50, whereinthe stereoscopic image data components are left eye image data and righteye image data.
 65. A method of formatting image data at a digitaldisplay interface part of a first audio-visual device for transport overa digital display interface between the first audio-visual device and asecond audio-visual device, the digital display interface fortransmitting uncompressed pixel information the method comprising:receiving image data; formatting the image data for transport over theinterface by: in a first mode, generating a stream of first dataelements which carry pixel data of a 2D image; and, in a second mode,generating a stream of second data elements which carry a multiplexedcombination of components of a stereoscopic image.
 66. The interfacepart according to claim 50, wherein the signaling information comprisesinformation for enabling the second audio-visual device to determine astereoscopic image format being used.
 67. A method of processing imagedata at a digital display interface part of an audio-visual device, thedigital display interface for transmitting uncompressed pixelinformation the method comprising: receiving formatted image data fromthe interface; extracting image data by: in a first mode, extractingpixel image data for a 2D image from a stream of first data elements;and, in a second mode, demultiplexing components of a stereoscopic imagefrom a stream of second data elements which carry a multiplexedcombination of components of a stereoscopic image.